SI Prefixes and Unit Conversions
Complete table of SI (metric) prefixes from yocto to yotta, with conversion factors and common chemistry applications.
| Prefix | Symbol | Factor | Decimal | Chemistry Example |
|---|---|---|---|---|
| yotta | Y | 10²⁴ | 1,000,000,000,000,000,000,000,000 | |
| zetta | Z | 10²¹ | 1,000,000,000,000,000,000,000 | |
| exa | E | 10¹⁸ | 1,000,000,000,000,000,000 | |
| peta | P | 10¹⁵ | 1,000,000,000,000,000 | |
| tera | T | 10¹² | 1,000,000,000,000 | TBq (terabecquerel) — radioactivity |
| giga | G | 10⁹ | 1,000,000,000 | GHz — spectroscopy frequencies |
| mega | M | 10⁶ | 1,000,000 | MPa (megapascal) — high pressures |
| kilo | k | 10³ | 1,000 | kJ (kilojoule) — enthalpy changes; kg (kilogram) — SI base unit of mass |
| hecto | h | 10² | 100 | |
| deca | da | 10¹ | 10 | |
| — | — | 10⁰ | 1 | Base unit (meter, gram, liter, mole) |
| deci | d | 10⁻¹ | 0.1 | dL (deciliter) — medical blood tests |
| centi | c | 10⁻² | 0.01 | cm (centimeter) — common lab measurements |
| milli | m | 10⁻³ | 0.001 | mL (milliliter) — lab volumes; mmol — millimoles |
| micro | μ | 10⁻⁶ | 0.000001 | μg (microgram) — trace element amounts; μM — micromolar |
| nano | n | 10⁻⁹ | 0.000000001 | nm (nanometer) — wavelengths of light (visible: 400–700 nm) |
| pico | p | 10⁻¹² | 0.000000000001 | pm (picometer) — atomic radii (H = 53 pm) |
| femto | f | 10⁻¹⁵ | 0.000000000000001 | fm (femtometer) — nuclear radii |
| atto | a | 10⁻¹⁸ | 0.000000000000000001 | attosecond — electron orbital timescales |
| zepto | z | 10⁻²¹ | 0.000000000000000000001 | |
| yocto | y | 10⁻²⁴ | 0.000000000000000000000001 | Mass of a proton ≈ 1.67 yg |
Important Notes
- The SI base unit of mass is the kilogram (kg), the only base unit with a prefix.
- In chemistry, the most commonly used prefixes are kilo (k), centi (c), milli (m), micro (μ), nano (n), and pico (p).
- To convert: multiply by the factor when going from prefixed to base unit, divide when going from base to prefixed.
- 1 Å (angstrom) = 100 pm = 0.1 nm. Angstroms are commonly used for bond lengths but are not an SI unit.
- Avogadro's number (6.022 × 10²³) is close to the yotta prefix (10²⁴), which is why 1 mole works as a practical laboratory quantity.